2) Use a rubber mallet to tap the stem bolt back down to free the expander or wedge plug. You may have to give it a few good whacks if your stem hasn't been moved in a while. If you don't have a rubber mallet, you can put a piece of hardwood or a thick piece of rubber on the head and use a regular hammer.
3) Position the stem where you want it and tighten the stem bolt as tight as you can get it. Don't over tighten it by using an extension on the wrench, just make it's as snug as you can get it.Note If you are raising your stem, make sure that you don't raise it too far. There is usually a line on the stem indicating the maximum height you can have the stem at. If not, the rule of thumb is to have the top slots in the side of the bottom of the stem (wedge type stem) or the highest point of the slant at the bottom of the stem on the wedge type stems at least an inch inside the fork (see fig.4 below).